The present invention relates generally to magnetic tape recorders, and more particularly to a recorder with improved cross-talk reduction.
For recording and/or reproducing broad-band signals, especially television signals, on/from magnetic tape, a high relative velocity can be obtained between the magnetic tape and the electromagnetic transformer or transformers, required for transfer, by disposing said transformers on a rapidly rotating head wheel or head drum, as is known from U.S. Pat. No. 3,414,683 and U.S. Pat. No. 3,591,732. In recent devices, the magnetic tape wraps around the head drum or a fixed bipartite drum, in which the head wheel revolves concentrically, in a helical fashion, so that the slowly moving magnetic tape is scanned in tracks running diagonally with respect to the lengthwise direction of the magnetic tape, by the electromagnetic transformer(s) located at the circumference of the head wheel, hereinafter called magnetic heads for short, thereby recording the signals to be stored on the magnetic tape as areas of varying magnetization. During playback, the latter are converted back into electrical signals and processed further.
German Patent Disclosure Document 24 11 402 teaches the transfer of signal and/or drive and/or supply voltages and/or powers without contact, from the fixed part of the magnetic tape recorder to the rotating head drum and back again. For inductive transfer, transformers are used whose coils are arranged pairwise concentrically with respect to one another, and with the primary winding of each being arranged in an annular magnetic core on the fixed part and the secondary winding being mounted likewise in an annular magnetic core on the rotating part, i.e., the head drum or head wheel. Various designs of rotary transformers which act as transfer devices are sufficiently known (German Patent 26 57 813; U.S. Pat. No. 4,364,098; U.S. Pat. No. 4,517,615; German Patent Disclosure Document 30 35 676; German Patent Disclosure Document 36 03 239). One important problem in designing a transformer-type transfer device is its crosstalk behavior. At least one pair of transformer is required for each type of signal and voltage transfer. The transformer pairs are usually mounted close together to save space. An axially and radially staggered arrangement of the rotary transformer pairs to reduce crosstalk as in German Patent 33 19 878 is usually not possible because of insufficient space and a plurality of transformer pairs.
To reduce magnetic scatter, therefore, in the past the transformer pairs were usually shielded from one another by short-circuit rings made of nonmagnetic efficiently electroconductive materials. (German Patent Disclosure Document 30 35 676; U.S. Pat. No. 4,517,615.) The electrical noise fields which radiate from the leads between the magnetic heads and the corresponding transformer windings so far have been reduced only by twisting the lead pair.